This invention relates to the field of testing for biological contaminants. Such contaminants may be found on equipment or other surfaces used in environments including food processing plants, hospitals, veterinary offices, and restaurants when a thorough cleaning has not been performed. Materials detected as indicators of contamination include, for example, viable bacterial cells, viruses, ATP, and protein. The ideal test for contamination would be effective, inexpensive, rapid, and easy to use and interpret.
Although pathogenic bacteria and viruses are clearly hazardous, the commonly used methods to detect them involve a number of steps, such as reagent preparation, reagent mixing, sample transfer, sample/reagent mixing, and incubation prior to reading results. Tests for these materials are not only time consuming but they also typically require the use of expensive and complicated equipment. Thus, routine testing of surfaces or equipment directly for bacteria or viruses is not practical in settings in which the testing is done by non-technical personnel and rapid results are demanded. As an alternative to testing for bacteria and viruses, many food processing plants use surrogate markers such as ATP and protein as indicators of contamination. Although these substances themselves are not usually harmful, they may serve as nutrient material for bacteria and are good general indicators of the effectiveness of cleaning.
ATP (adenosine triphosphate) is a chemical common to all living organisms. The presence of significant levels of ATP on a surface indicates that cleaning was incomplete and that bacteria may be present. Because hygiene monitoring by ATP detection is common, relatively inexpensive, rapid, and effective, it is widely used. However, detecting ATP suffers from certain limitations that restrict its utility, in that it involves the use of a relatively expensive instrument and may involve transporting samples to a central laboratory.
Clearly tests for protein as evidence of contamination provide an attractive alternative to direct testing for bacteria and viruses or for ATP detection. Unfortunately, many examples of current methods for protein determination, which can serve as an indicator of a contaminated surface involve on-site reagent preparation due to stability problems, along with multiple transfer steps, incubation periods, and/or involve highly subjective color changes which make interpretation difficult, and/or require the use of complex instrumentation or specially trained personnel. Examples of common protein determination methods are described in Stoscheck, Quantitation of Protein, in METHODS IN ENZYMOLOGY Vol. 182, pp.50-68, 1990. Among the variants of basic protein detection methods are methods using colloidal forms of COOMASSIE® blue stain to detect proteins in gels such as polyacrylamide electrophoresis gels. Such methods are described, for example, in Neuhoff et al., Electrophoresis 6:427-488, 1985 and Neuhoff et al., Electrophorests 9:255-262, 1988. In addition to the conventional protein assay methods referenced above, a combination cleaning and protein staining composition is described in Winicov et al., U.S. Pat. No. 5,424,000, entitled ACID CLEANINGS AND STAINING COMPOSITIONS, issued Jun. 13, 1995. The solutions preferably include phosphoric, sulfuric, and nitric acids, and Acid Violet 19 dye.
A number of different self-contained sampling/testing devices employing certain assays have been described. Examples of such assays include sampling for bacterial contaminants in food processing plants, the sampling for contamination of the environment by heavy metals such as lead, and the collection of specimens from a patient to test for microorganism infection.
Specific examples of self-contained sampling/testing devices include Nason, U.S. Pat. No. 5,266,266, issued Nov. 30, 1993, and Nason, U.S. Pat. No. 4,978,504, issued Dec. 18, 1990, both entitled SPECIMEN TEST UNIT; Nason, U.S. Pat. No. 4,707,450, issued Nov. 17, 1987, entitled SPECIMEN COLLECTION AND TEST UNIT; Numa, U.S. Pat. No. 5,726,062, issued Mar. 10, 1998; and Tobin, U.S. Pat. No. 3,792,699, issued Feb. 19, 1974. The use of protein error dyes to estimate protein content in urine is disclosed in Keston, U.S. Pat. No. 3,485,587, entitled PROTEIN INDICATOR. All of which are hereby incorporated by reference in their entireties including drawings. However, all of the aforementioned devices suffer from the same drawbacks noted above.
Thus, as no self-contained device or methodology exists that is inexpensive, rapid, and easy to use and interpret, there exists a need in the art for such a device relevant to the detection of biological contamination. The present invention fulfills these needs, and provides other related advantages.